Conventionally, motors are integrally provided with protective devices such as a bimetal, a PTC (positive temperature coefficient) device, etc. If the motor generates heat extraordinarily during its operation, a certain condition of device temperature, device resistance, etc. are satisfied for the protective devices to break an electric circuit of the electric motor. Thus, the electric motor stops being energized, to be prevented from being burnt.
However, when the above-mentioned protective device is located in a proximity to a main body of the electric motor, a size of the electric motor increases, to upsize an entire body of an apparatus provided with the motor. JP-11-164472-A discloses a motor control apparatus that calculates an estimated temperature of the motor without being provided with the above-mentioned protective device. Specifically, the motor control apparatus includes a control unit for controlling the motor that calculates an estimated temperature of the motor by using an energizing voltage and time applied to the motor, and a previously estimated temperature.
The motor control apparatus according to JP-11-164472-A stops the operation of the motor when the estimated temperature becomes equal to or larger than a predetermined overheat prevention temperature. The motor control apparatus keeps stopping the operation of the motor until the estimated temperature decreases to an overheat prevention release temperature.
However, the above-mentioned protective devices are used to prevent the motor from being burnt, the motor control apparatus can forcedly stop the operation of the motor if the protective device satisfies a certain condition. The motor control apparatus according to JP-11-164472-A forcedly stops the operation of the motor once the estimated temperature exceeds the overheat protection temperature.
Thus, in such a case that the motor is forcedly stopped while the motor is driving a power window apparatus to its closing side in an automatic mode, the window glass is stopped at a middle position before it completely closes at a full close position. That is, the motor control apparatus has an incommodity to stop the operation before completing a continuous set operation such as a closing operation of the power window apparatus.
In this case, the window glass is stopped at the half-open middle position even when a driver or a passenger attempts to close the window glass fully in parking the vehicle. In a case that the power window apparatus is provided with a pinch-free function, the window glass can keep pinching a hand, etc., when the motor of the power window apparatus is forcedly stopped.